There is an increased demand for chalcogenide materials containing copper (Cu), zinc (Zn), tin (Sn), sulfur (S) and/or selenium (Se), such as Cu2ZnSn(S/Se)4 (CZTS), for use as absorber layers in solar cells. In order to fabricate CZTS absorber layers for next generation low cost solar cells, the production of whisker and dendrite free controlled thin films of Zn will be required. A whisker, for example, is a protrusion of a metal bar or needle which is usually submicrometer to a few micrometers in length, and which causes shorting in the device. See, for example, J. J. Scragg et al, “Synthesis and Characterization of Cu2ZnSnS4 Absorber Layers by an Electrodeposition-Annealing Route,” Thin Solid Films, 517(7), pgs. 2481-2484 (2009), M. Kurihara et al., “Kesterite Absorber Layer Uniformity From Electrodeposited Pre-Cursors,” Phys. Status Solidi, C6 (5) 1241-1244 (2009) and T. K. Todorov et al., “High-Efficiency Solar Cell with Earth-Abundant Liquid-Processed Absorber,” Advanced Materials, 22, 1-4 (2010). In addition, controlled Zn thin films will be in high demand for applications such as corrosion resistance layers on ferrous materials, as well as on decorative parts, electronic materials and automotive parts. See, for example, M. S. Pereira et al., “The Influence of Sorbitol on Zinc Film Deposition, Zinc Dissolution Process and Morphology of Deposits Obtained from Alkaline Bath” J. Appl. Electrochem., 36, 727-732 (2006) and M. Li et al., “Effect of Additives on Electrodeposition of Nanocrystalline Zinc from Acidic Sulfate Solutions,” J. Electrochem. Soc., 154 (11), D567-D571 (2007).
Many current Zn thin film plating techniques, however, require high plating temperatures and contain very toxic materials like cyanide and ammonium, or use an alkaline solution which is a potential source of oxygen as an impurity in the deposit. Other Zn thin film plating techniques have low plating efficiency or use an acidic bath that is only for Zn-alloys with metals such as nickel (Ni) and others. Commercial galvanizing methods are mainly applied for thick layers of Zn deposit and are not suitable for thin film fabrication.
Therefore, improved techniques for controlled Zn thin film plating would be desirable.